1. Field of Invention
The present invention relates to a photo detector. More particularly, the present invention relates to a photo detector having a low temperature poly-silicon (LTPS) material for a display panel.
2. Description of Related Art
FIG. 1 is a schematic diagram illustrating a traditional PIN photo diode 100. A PIN photo diode 100 comprises an N-type semiconductor region 102, a P-type semiconductor region 104 and an intrinsic semiconductor region 106 between the N-type semiconductor region 102 and the P-type semiconductor region 104. When light irradiates the intrinsic semiconductor region 106, the holes (h+) and electrons (e−) generated by the photoelectric effect would respectively move to the P-type semiconductor region 104 and the N-type semiconductor region 102, thus generating a photoelectric current. It is well known that by measuring such photoelectric current, the PIN photo diode 100 could be used as a photo detector.
Generally, photo detectors manufactured by the LTPS thin film transistor (TFT) technique have the disadvantage of low photosensitivity. The low photosensitivity is because the thickness of the substrate used for photo-absorption is only about 50 nm. In addition, the traditional PIN photo diode suffers from the problem of excessive dark current due to its manufacturing process. Moreover, in consideration of the manufacturing process, a CMOS process that could carry out the implantation of the n+ ion and p+ ion at the same time would increase the complexity of the manufacturing process of the PIN photo diode. Therefore, the known solutions for increasing or improving the performance of photo detectors could not be completely adapted to or compatible with the current TFT manufacturing process of the display device.